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<div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="34_1_1_1"><b>per </b></a><a class="txt" onclick="hs(this)" href="javascript:()"><b>cases </b></a><span class="hide"><a NAME="E1:34_1_1_1"/>
(  not <font color="Maroon">SF</font> is <a href="xboole_0.html#V1">empty</a> or <font color="Maroon">SF</font> is <a href="xboole_0.html#V1">empty</a> )
 </span>;<br/><div class="add"><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="34_1_1_1_1"><b>suppose </b></a><a NAME="E1:34_1_1_1_1"/><i><font color="Green">E36</font></i>: 
not <font color="Maroon">SF</font> is <a href="xboole_0.html#V1">empty</a>
 ;<br/><div class="add"><a NAME="E2:34_1_1_1_1"/>
<span class="p1"><a href="closure2.html#K4" target="_self">|:</a><span class="default"><font color="Maroon">SF</font></span><a href="closure2.html#K4" target="_self">:|</a></span> is    <a href="pboole.html#M4">ManySortedSubset</a> of  <a href="mssubfam.html#K7">bool</a> <font color="Maroon">M</font>
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="34_1_1_1_1_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">i</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="pboole.html#D5">PBOOLE:def 5</a>,<a class="ref" href="pboole.html#D23">PBOOLE:def 23</a><br/>

<b>assume </b><a NAME="E1:34_1_1_1_1_1"/><i><font color="Green">E39</font></i>: 
<font color="Maroon">i</font> <a href="hidden.html#R2">in</a> <font color="Maroon">I</font>
 ;<br/>

<a NAME="E2:34_1_1_1_1_1"/><b>then </b><i><font color="Green">E40</font></i>: 
<span class="p1"><a href="closure2.html#K4" target="_self">|:</a><span class="default"><font color="Maroon">SF</font></span><a href="closure2.html#K4" target="_self">:|</a></span> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font> <a href="hidden.html#R1">=</a> <span class="p1">{<span class="default"> <span class="p2">(<span class="default"><font color="Olive">x</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font></span>)</span> where <font color="Olive">x</font> is    <a href="closure2.html#M1" target="_self">Element</a> of  <a href="closure2.html#K2" target="_self">Bool</a> <font color="Maroon">M</font> : <font color="Olive">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">SF</font> </span>}</span> 
 
<b>by </b><i>, </i>;<br/>
<b>thus </b><a NAME="E3:34_1_1_1_1_1"/>
<span class="p1"><a href="closure2.html#K4" target="_self">|:</a><span class="default"><font color="Maroon">SF</font></span><a href="closure2.html#K4" target="_self">:|</a></span> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><a href="mssubfam.html#K7">bool</a> <font color="Maroon">M</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font>
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="34_1_1_1_1_1_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E1:34_1_1_1_1_1_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="closure2.html#K4" target="_self">|:</a><span class="default"><font color="Maroon">SF</font></span><a href="closure2.html#K4" target="_self">:|</a></span> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font>
 ;<br/>

<b>then consider </b><font color="Maroon">a</font> being    <a href="closure2.html#M1" target="_self">Element</a> of  <a href="closure2.html#K2" target="_self">Bool</a> <font color="Maroon">M</font><b> such that </b><br/><a NAME="E3:34_1_1_1_1_1_1"/><i><font color="Green">E45</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">a</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font>
 <b>and </b><br/><a NAME="E4:34_1_1_1_1_1_1"/>
<font color="Maroon">a</font> <a href="hidden.html#R2">in</a> <font color="Maroon">SF</font>
 <b>by </b><i/>;<br/>
<a NAME="E5:34_1_1_1_1_1_1"/>
<font color="Maroon">a</font> <a href="pboole.html#R2">c=</a> <font color="Maroon">M</font>
 
<b>by </b><i><a class="ref" href="pboole.html#D23">PBOOLE:def 23</a></i>;<br/>
<a NAME="E6:34_1_1_1_1_1_1"/><b>then </b>
<font color="Maroon">x</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">M</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font>
 
<b>by </b><i>, , <a class="ref" href="pboole.html#D5">PBOOLE:def 5</a></i>;<br/>
<a NAME="E7:34_1_1_1_1_1_1"/><b>then </b>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="zfmisc_1.html#K1">bool</a> <span class="p1">(<span class="default"><font color="Maroon">M</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font></span>)</span>
 
;<br/>
<b>hence </b><a NAME="E8:34_1_1_1_1_1_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><a href="mssubfam.html#K7">bool</a> <font color="Maroon">M</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font>
 <b>by </b><i>, <a class="ref" href="mboolean.html#D1">MBOOLEAN:def 1</a></i>;<br/>


</div><b>end;</b></div>


</div><b>end;</b></div><b>hence </b><a NAME="E3:34_1_1_1_1"/>
<span class="p1"><a href="closure2.html#K4" target="_self">|:</a><span class="default"><font color="Maroon">SF</font></span><a href="closure2.html#K4" target="_self">:|</a></span> is   <a href="mssubfam.html#NM1">MSSubsetFamily</a> of <font color="Maroon">M</font>
 ;<br/></div><b>end;</b></div><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="34_1_1_1_2"><b>suppose </b></a><a NAME="E1:34_1_1_1_2"/>
<font color="Maroon">SF</font> is <a href="xboole_0.html#V1">empty</a>
 ;<br/><div class="add"><a NAME="E2:34_1_1_1_2"/><b>then </b>
<span class="p1"><a href="closure2.html#K4" target="_self">|:</a><span class="default"><font color="Maroon">SF</font></span><a href="closure2.html#K4" target="_self">:|</a></span> <a href="pboole.html#R6">=</a>  <a href="pboole.html#K1">[0]</a> <font color="Maroon">I</font>
 <b>by </b><i/>;<br/><b>hence </b><a NAME="E3:34_1_1_1_2"/>
<span class="p1"><a href="closure2.html#K4" target="_self">|:</a><span class="default"><font color="Maroon">SF</font></span><a href="closure2.html#K4" target="_self">:|</a></span> is   <a href="mssubfam.html#NM1">MSSubsetFamily</a> of <font color="Maroon">M</font>
 <b>by </b><i><a class="ref" href="mssubfam.html#T31">MSSUBFAM:31</a></i>;<br/></div><b>end;</b></div></div><b>end;</b></div>

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